The present invention relates to a piezoelectric actuator subjected to bending displacement by sensing a reducing gas such as a carbon monoxide gas, a hydrogen gas, etc., and more particularly to a piezoelectric actuator suitable for operating valves, etc. by sensing a reducing gas such as a carbon monoxide gas, a hydrogen gas, etc. in an apparatus or equipment which may generate such a reducing gas.
Exhaust gases discharged from internal engines, combustion apparatuses, etc. may contain reducing gases such as a carbon monoxide gas, a hydrogen gas, etc. Since the reducing gases are harmful to human beings and cause air pollution, the generation of such reducing gases should be suppressed. For this purpose, a reducing gas sensor is used, but a widely used reducing gas sensor is constituted separately from an actuator, so that the actuator is operated in response to an output signal of the sensor to drive a control valve or to change combustion conditions. However, with such a separate structure, wiring of the reducing gas sensor, an actuator, a controller (for instance, computer), etc. is extremely complicated, making the overall structure of the apparatus complicated, and making it difficult to check and repair the apparatus.